1. Field of the Invention
This invention relates to a valve and a method for opening or closing fluid flow through an annular conduit by the utilization of a flexible diaphragm.
2. Description of the Prior Art
The control of fluid flow by valves is one of the more voluminous areas of prior art. Valve constructions heretofore employed have generally utilized either a poppet configuration or a slide valve. In the poppet valve, a valving member is moved directly away from a valve seat. In the sliding valve construction, the valving member is moved parallel to a seat, generally of an elastomeric material, to open up the fluid passage. With either type of common valve construction, a significant amount of relative movement of the two elements comprising the valve must be accomplished in order to convert the valve from its fully closed to its fully open position. Moreover, as the valve is partially opened, the rush of fluid out of the restricted opening generally has adverse erosion effects on the elastomeric seal materials which surround the valve opening.
Additionally, in all common forms of valves, the greater the pressure differential that exists across the valve in the closed position, the greater is the force required to effect the opening of the valve, due to the frictional drag of the valve members across the sealing elements in the case of a slide valve, and due to the pressure forces exerted on a poppet valve as it attempts to move away from its seat.
In many fluid valving applications, there is a definite need for a valve which will move from a completely closed to a completely open position with a small amount of relative movement of the two elements of the valve. Moreover, the rapidity of the movement to a fully opened position reduces the tendency of the trapped fluid to rush through the partially opened valve with extreme velocity, thus eliminating the adverse erosive effects encountered in valves of conventional configuration.
There is a particular need for an improved pilot valve for fluid actuators employed in a number of industrial applications. Such pilot valves should be capable of being moved from a fully closed to a fully opened position by a very small relative movement of the valve elements.
Moreover, it is extremely important that there be a minimum of fluid pressure induced resistance to the relative axial movement of the valve elements during the opening or closing movements of the valve elements.
Additionally, when the valve is in its closed position, the fluid outlet passage should preferably be connected to a vent or bleed passage to insure the drainage of all of the operating fluid therefrom prior to the next opening of the valve.